"What distinguishes these past few months from [previous rallies] is that the excitement has been generated not from government policies, but from corporate activity," says Jacobson, whose funds year to date are up 86% and 110.1%, respectively.

143 Companies Make Restructuring Plans

Japanese corporations have begun to do what counterparts in Europe and the U.S. have been doing for quite some time: They're cutting costs by downsizing, exiting unprofitable businesses and merging with one another in hopes of boosting profitability.

Sony, NEC and Mitsubishi Chemical are among the big companies leading the charge. Overall, at least 143 companies announced plans to restructure in the first five months of the year, according to brokerage Morgan Stanley Dean Witter.

Based on the current pace, mergers in Japan this year will represent 4% of Japan's total market capitalization, Jacobson says. Historically, mergers each year have accounted for just 1% of market capitalization.

The Japanese government is encouraging mergers by allowing companies to use their stock as currency to do deals. "That's taken for granted in the U.S., but this will make company stock a fiat currency, which gives Japanese executives another incentive to boost the value of their stock and add shareholder value," Jacobson says.

To be sure, compared with restructuring activity in Europe, Japan is still far behind. And "from a Westerner's point of view, it's a frustratingly slow process still," says Peter Kirkman, manager of the TCW Galileo Japanese Equities fund, which is up more than 60% over the last 12 months.

"But I think the mistake the bears have made in this market is focusing too much on the top-down story [the economy] and not enough on the bottom-up" or corporate reform, he says.

Another difference between this rally and previous false starts: Yields on Japanese government bonds, although above their lows of last fall, still are far below the levels of the early and mid-1990s, when they provided a reasonable alternative to stocks. A 10-year government bond now yields just 1.7%.

As older bonds and long-term bank certificates of deposit mature, many analysts say, Japanese households will have no choice but to invest some of that money in stocks if they want their capital to grow.

All in all, says Jacobson, "in the last few months I've been pounding tables at meetings saying that this [rally] is different from a lot of the previous head-fakes."

Still, he admits, there are roadblocks on Japan's path to recovery, not the least of which is the state of the economy. Though it grew a surprising 1.9% in the first quarter, Jacobson and Kwak expect the economy to contract a bit in the second half of the year.

"The economy is still very fragile," Jacobson says.

Restructurings and Pressure on Economy

Ironically, the very thing that has investors confident about stocks--corporate restructuring--could damage the economy in the short term.

"Restructuring can put downward pressures on an economy," Kirkman says. He notes that Japanese companies walk a fine line between boosting investor confidence (and the long-term health of the economy) by slashing unnecessary jobs, and hurting consumer confidence and spending (and the short-term health of the economy) by cutting jobs too quickly.

Another irony: As foreign investors buy yen to invest in Japanese stocks, they're driving the currency's value up. A stronger yen will make Japanese exports more expensive abroad.

The yen, now at just under 117 to the dollar, is at its strongest level since February.